An electromagnetic actuator for actuating a gas-reversing valve on a piston internal combustion engine essentially comprises two electromagnets, the pole faces of which are arranged so as to face each other at a distance. Between these two electromagnets, an armature can move back and forth counter to the force of at least one restoring spring, such that with a correspondingly controlled alternating feed of current to the two electromagnets, the gas reversing valve is alternately moved to the closed position or the opened position.
The alternating current feed occurs such that power is turned off to the electromagnet, in this case the closing magnet, which keeps the armature in one end position, for example the closed position of the valve. The armature thus can detach itself from the pole face with the aid of the respectively pre-stressed opening spring and is accelerated in the direction of the other magnet, which in this case is the opening magnet. The opening magnet is then supplied with current, so that the armature is securely captured while it passes through the center position during the approach to the pole face of the opening magnet and is held for the predetermined opening interval against the pole face. In the process, the valve spring that functions as the restoring spring is compressed, so that once the current to the opening magnet is turned off, the movement course is the same as for the closed position. The electromagnets are identical in size and have the same layout with respect to capacity, e.g. as disclosed in German patent document DE 197 14 496 A1. In addition, it has been standard procedure, up to now, to equip all gas-reversing valves of a piston internal combustion engine with identical actuators.
However, it has turned out that a higher electrical capacity is required for opening the gas-exhaust valves than for opening the gas intake valves. This is due to the fact that losses caused by the pressure differences between combustion chamber and exhaust port during the opening of the gas exhaust valve, which act upon the valve in closing direction, must be compensated if the engine load increases. To meet this requirement, it has been suggested according to German patent document DE 199 07 850 A1 that actuators be assigned to the gas exhaust valves, for which the electromagnets have a larger pole face than the electromagnets of the actuators assigned to the gas intake valves. However, the so-called “identical parts principle” for the actuators was maintained for this solution, meaning each actuator comprises identical magnets having identical pole faces.